# Description
I wanted to just use a state machine purely in GDscript, as simply as possible, but with states, transitions, hooks, and conditions/triggers to change states

- States: the FSM will always be in a state. It will change to another state with the transitions, following the first transaction, having the current state as a source, that matches the conditions/trigger
- Transition: a transition will allow the FSM to change from one state to another when, at each update
  - The transition is fully matched the (optional) trigger has been called
  - The (optional) conditions has all been met
  - A transition is composed of
    - A state source
    - A state destination
    - An optional list of conditions
    - An optional trigger
- Transition source: in order to reduce the amount of code to type for transitions, there are some helpers. source can be a string (STATE), or it can be an array:
  - STATE: any known state (the easy one)
  - "*": all the states (including the destination)
  - ^STATE: all the states but STATE. e.g. "^hurt" => it will match, for source, all the states except "hurt"
  - -STATE: remove STATE from the previous states added (when source is an array). e.g. ["*", "-idle", "-hurt"] => it will match, for source, all the states except "idle" and "hurt"
- Trigger: a transition can be mapped to 0 or 1 trigger. A trigger is emitted by calling the "trigger" method, and the trigger will be treated at the next update and then forgotten
- Condition: a condition is just the callback of a method returning a boolean. It can be the name of the method, or it can prefixed by "!" to get the reverse boolean

# TODO
- Maybe optimize the whole thing

# How to use
- Add it to your project : https://docs.godotengine.org/en/stable/tutorials/plugins/editor/installing_plugins.html#enabling-a-plugin
```
    mkdir -p addons
    cd addons
    git submodule add ssh://git@git.abxy.fr:212/groug/godot_simple_state_machine.git
```

- Add the custom StateMachine node (name it "StateMachine" for the purpose of the example)
- Initialize the states, initial state and conditions:
```
	$StateMachine.add_state("idle")
	$StateMachine.add_state("hurt")
	$StateMachine.add_state("dead")
	$StateMachine.set_init_state("idle")
	$StateMachine.add_transition("idle", "hurt", [], "fire")
	$StateMachine.add_transition("hurt", "dead", ["has_stuff_been_handled", "is_dead"])
	$StateMachine.add_transition("hurt", "idle", ["has_stuff_been_handled"])
```

- Trigger an event
```
	$StateMachine.trigger("fire")
```

- Add a condition: it's just a func returning a bool
```
    def has_stuff_been_handled():
        return true
```

- Add callbacks for state entering/update/exiting: just add the state name in on_XXXXX_state_YYYY()
```
    func on_idle_state_enter():
        pass

    func on_idle_state_update(delta):
        pass

    func on_idle_state_exit():
        pass
```
- Enabling debug mode (logs when changing states)
```
    $StateMachine.set_debug_enabled(true)
```

- Get the current state
```
    $StateMachine.get_current_state()
```

- Get the last known state (before the current one)
```
    $StateMachine.get_last_state()
```

# Credits
icon: made by Freepik from https://www.flaticon.com, license: Creative Commons BY 3.0